1. Field of the Invention
The present invention relates to a multi-nozzle ink jet recording device and a recording method for reliably forming high-quality images by deflecting ejected ink droplets using a charging electric field and a deflector electric field.
2. Description of the Related Art
Japanese Patent Publication No. SHO-47-7847 discloses a conventional ink jet recording device that forms images on a recording sheet. The device is formed with a plurality of nozzles aligned in a line in a widthwise direction of the recording sheet. Ink droplets are ejected from the nozzles and impact on the recording sheet and form dots thereon while the recording sheet is moved in a sheet feed direction perpendicular to the widthwise direction. The ejected ink droplets are uniform in their size and each is separated from the other.
The recording device also includes electrodes that generate a charging electric field and a deflector electric field. The charging electric field charges the ejected ink droplets based on a recording signal, and the deflector electric field having a uniform magnitude changes a flying direction of the charged ink droplets along the widthwise direction as needed, thereby controlling the impact positions of the ink droplets with respect to the widthwise direction and forms the dots on exact target positions. The target portions are usually determined by a coordinate system defined on the recording sheet.
There has been also proposed a nozzle array where a plurality of nozzles are formed in an arrayed manner, which improves recording speed. Also, there has been increased demand for obtaining higher-resolution images. Increasing the resolution of images requires a smaller distance between adjacent two nozzles so as to obtain a sufficiently high nozzle density. However, it is difficult to provide electrodes for generating the charging electric field for each of the plurality of nozzles arranged in such a high nozzle density because of the structural reasons.
In order to overcome the above problems, it is conceivable to form electrodes with a simple straight shape common to all of the plurality of nozzles. Such common electrodes would realize a high nozzle density, reduce manufacturing cost of the ink-jet recording device, and improve reliability thereof.
However, there are following problems in providing the common electrodes.
First, because the nozzle line extends in the widthwise direction as described above, the common electrodes need to extend in the widthwise direction also in order to change the flying direction of the ink droplets. However, in this case, the flying direction of the ink droplets will be changed along the sheet feed direction, rather than the widthwise direction. There is no advantage or reason to change the flying direction along the sheet feed direction in this type of recording device.
On the other hand, when the nozzle line is arranged to extend in the sheet feed direction rather than the width wise direction, common electrodes extending in the sheet feed direction will change the flying direction along the widthwise direction. However, images cannot be formed in this arrangement.
Therefore, both the nozzle line and the common electrodes are required to extend angled with respect to the widthwise direction without being parallel with the sheet feed direction.
However, when the nozzle line is angled in this manner, a position of each nozzle changes from its original position with respect to both the sheet feed direction and the widthwise directions, and so the impact position of the ink droplet also changes. As a result, the impact position will shift from the target position defined by the coordinate system, and positional error occurs.
In addition, because the common electrodes also are angled with respect to the widthwise direction so as to extend parallel with the nozzle line, the deflect direction of the ink droplet is angled with respect to the widthwise direction. If it is possible to individually control the deflection amount and ejection timing of ink droplets from each nozzle, it may be possible to adjust such a positional error. However, when the common electrodes are used, the deflection amount and ejection timing are common to all nozzles, so that it is difficult to control all ink droplets to impact on exact target positions.
It is therefore an objective of the present invention to overcome the above-described problems and also to provide a multi-nozzle ink-jet recording device having a charging electrode and deflector electrode, which are common for all nozzles, and capable of controlling ink droplets ejected from the nozzles to accurately hit on target impact positions in a recording coordinate with a predetermined resolution, and also to provide a recording method thereof.
In order to achieve the above and other objectives, there is provided a multi-nozzle ink jet recording device including a print head, ejection means, a pair of electrodes, generating means, and control means. The print head is formed with an orifice line extending in a line direction and including a plurality of orifices aligned at a uniform pitch. The ejection means ejects ink droplets through the plurality of orifices. The ink droplets have a uniform shape and being separated from one another. The pair of electrodes are common to all the plurality of orifices. The generating means generates a charging electric field and a deflecting electric field at the same time by applying a voltage to the pair of electrodes. The charging electric field is generated near the orifices, has a magnitude that changes at an ink-ejection frequency, and charges the ink droplets. The deflecting electric field has a constant magnitude and deflects a flying direction of the ink droplets. The controlling means controls the ejection means to eject the ink droplets at a uniform ejection interval onto all grid corners of grids in a coordinate system defined on a recording medium having a width in a widthwise direction and a length in a lengthwise direction perpendicular to the widthwise direction.
There is also provided a multi-nozzle ink jet recording device including a print head, ejection means, a pair of electrodes, applying means, and controlling means. The print head is formed with an orifice line extending in a line direction and including a plurality of orifices aligned at a uniform orifice pitch. The ejection means ejects ink droplets through the plurality of orifices at an ink-ejection frequency onto a recording medium having a width in a widthwise direction and a length in a lengthwise direction perpendicular to the widthwise direction. The line direction has an angle xcex8 with respect to the lengthwise direction. The pair of electrodes are common to all the plurality of orifices and extending in the line direction while interposing the orifice line therebetween in plan view. The applying means applies a voltage to the pair of electrodes. The pair of electrodes generate a charging electric field and a deflecting electric field between the electrodes when applied with the voltage. The charging electric field has a magnitude that changes at the ink-ejection frequency and charges the ink droplets. The deflecting electric field has a constant magnitude and deflecting a flying direction of the ink droplets charged by the charging electric field. The controlling means controls the voltage applied to the electrodes such that the ink droplets deflected by the deflecting electric field impact on all grid corners of grids in a coordinate system defined on the recording medium, and that ink droplets ejected through a single one of the plurality of orifices and deflected by the deflecting electric field impact on one of n scanning lines extending in the lengthwise direction.
Further, there is provided a printing method using a multi-nozzle ink jet recording device including components. The components includes a print head formed with a orifice line extending in a line direction and including a plurality of orifices; ejection means for ejecting ink droplets through the plurality of orifices, the ink droplets having a uniform shape and separated from one another; a pair of electrodes common to all the plurality of orifices; and generating means for generating a charging electric field and a deflecting electric field at the same time by applying a voltage to the pair of electrodes, the charging electric field being generated near the orifices and having a magnitude that changes at an ink-ejection frequency and charging the ink droplets, the deflecting electric field having a constant magnitude and deflecting a flying direction of the ink droplets. The method includes the step of controlling the components to eject the ink droplets at a uniform ink-ejection frequency onto all grid corners of a rectangular coordinate system defined on a recording medium.
There is also provided a printing method using a multi-nozzle ink jet recording device including components that includes: a print head formed with a orifice line extending in a line direction and including a plurality of orifices aligned at a uniform orifice pitch; ejection means for ejecting ink droplets through the plurality of orifices, the ink droplets having a uniform shape and separated from one another; a pair of electrodes common to all the plurality of orifices; and generating means for generating a charging electric field and a deflecting electric field at the same time by applying a voltage to the pair of electrodes, the charging electric field being generated near the orifices and having a magnitude that changes at an ink-ejection frequency and charging the ink droplets, the deflecting electric field having a constant magnitude and deflecting a flying direction of the ink droplets. The method includes the step of controlling the components to eject the ink droplets at a uniform ink-ejection frequency onto all grid corners of a non-rectangular coordinate system defined on a honeycomb-shaped recording medium.